Manufacture of fiber board



Patented Aug. 14, 1928.

UNITED STATES PATENT OFFICE.

ROBERT A. man, NORFOLK, VIRGINIA.

muracruan OF FIBER BOARD.

No Drawing. Application filed October 27, 1922, Serial No. 597,419.Renewed January 19, 1928.

The present invention relates particularly to the manufacture of fiberboard although it, will be understood that the same is applicable alsoto the manufacture of ot her fiat molded articles from pulp and slmllarmaterials.

In my co-opending applicatlon I filed October 17, 1922, Serial No.595,215 is described a process of makin pulp which can be brieflydescribed as fol ows: Qane material including cane and bamboo 1Sdigested under pressure in an aqueous solution containing preferablyzinc sulfate, sodium sulfate and potassium sulfate, after wh ch the canematerial is removed from the digester, preferably washed and can then beconverted into pulp by being run through a pulper and a Jordan or apuler and a beater engine. The pulp produce in accordance with said processis particularly advantage ous for use in the present invention, althoughit is to be understood that other kinds of pulp can be employed, eitherwood pulp of the ordinary kind, or recovered pulp fromrepulping usedpaper. In the present invention, a liquid flowable pulp constitutes thestarting material, this containing,

readily flowable condition.

In the first step of the process, according to the present invention, anamount of the from side to side or lengthwise, if desired,

in order to fibers.

The suction is continued until substantially all of the free water ofthe pulp is removed. A cloth is then placed on the top of the layer ofpulp, and the sides of the produce a better felting of the box are thenlifted off. Unless cloth has been used in the bottom of the box-sievebeforerunning in the pulp, the bottom of the box-sieve containing thepulp, is then as is usual, a sufficient amount of aqueous liquid such aswater, to be in a inverted upon suitable table or bench and a" cloth isplaced on top of the pulp. The entire package contaimng the pulp withthe cloth above and below the same is then wrapped 1n a fine Wire meshscreen, for example, 70 mesh screen, and the package containing the wetboard is then placed in a perforated tray of which the bottom is rigidand perforated with numerous small holes. This may take the form of aperforated galvanized iron box, of a size adapted to fit the packagecontaining the sheet of wet pulp. A board or rigid member' is thenplaced upon the package containing the wet pulp and the same is thensubjected to heavy pressure in order to squeeze out as much as possibleof the water contained in the pulp board. This leaves a pulp board whichis still damp but which is rigid enough and strong enough to be handledto some extent. This is then placed between foraminous rigid plates,which are then clamped together and the same then run into a drying ovenwhere the damp pulp board is dried While being held between theforam'inous rigid plates. If desired any suitable waterproofing agent,such as those commonly used in the art, may be applied to the pulp boardbefore this drying operation, or the dried pulp board may be dipped intoa solution of water-proofing agent, and again dried between the foraminous rigid plates.

A suitablecovering such as paper may then be glued upon one or bothsides of the pulp board in the usual manner. The boards produced inaccordance with this invention are more uniform and are materiallystronger than pulp boards made according to any prior processes withwhich I am familiar.

It will be understood that a suitable binder either of a water solubleor water insoluble nature can be incorporated with the pulp at anysuitable stage of the operation. a binder of a water insoluble nature isused, this may be incorporated with the pulp in the pulper or Jordan orbeater engine. If a water soluble binder such as glue is to be used,this can be added to the liquid pulp in the box sieve used in the firststage of the molding operation. Since such a method would ordinarilyinvolve considerable waste of binder, it is more advisable to spray thepulp board during or just after the suction operation and before thepressing operation.

The binder ma in some cases also serve as a water roo g agent.

During t e first filtration, in the box sieve, the wire gauze formin thebottom of the box sieve should be suitably supported, in order toprevent the same from bulging down materially in the center which woullead to the production of boards thicker at the center than at theedges.

' I have above referred to the use of cane fiber as bein the preferredmaterial for making the fiber boards. It will be understood however,that this material can be used alone or mixed with other kinds of pulp,including ordinary wood pulp, and recovered pulp, from repulping usedpaper. A particular mixture which has been shown to be very advantageousand cheap is a mixture 0 repulped brown paper waste and the cane pulpabove described.

It will be understood that the wrapping of the fabric and of wire gauzecan be removed at any time after the pressing operation. Ordinarily, Iremove the said wrappings directly after the pressing operation, andbefore placing the dampboards in the drying frames.

What I claim is:

1. A process of making fiber board which comprises running into boxsieve, an amount of a liquid pulp containing a large amount of aqueousliquid and a small amount of pulped digested cane material, such amountof liquid pul containing a predetermined weight of said cane material,removing in the liquid state the major part of the aqueous liquid insuch pulp, by suction, encasing the residual semi-dried pulp material ina fabric, and also encasing the same in a fine wire mesh exteriorcasing, and supporting the package on a rigid perforated plate, andapplying a uniform mechanical pressure on the top of said package tosqueeze out more of the aqueous liquid, until a rigid wet pulp board isproduced, placing such rigid wet board between non-flexible perforatedmembers and clamping the same together, and drying the board while ,heldbetween said members under sufiicient pressure to prevent substantialwarping, whereby a rigid fiat board structure is roduced.

2. In the manu acture of pulp articles, the steps of placing in a boxsieve having vertical side walls, an amount of liquid fiber pulpcontaining a predetermined amount of actual dry pulp, removing theliquid material therefrom while leaving the whole of the solid pulp anddrying the product while clamped to prevent warping.

3. In the making of pulp board, the steps of forming a wet pulp boardand pressing the same while encased in fabric and in fine wire meshscreening, to eliminate a major part of the aqueous liquid therein, thendrying the pressed boards while closely held between rigid perforatedplates to prevent warping.

4. A process of making fiber board which comprises running into boxsieve, an amount of liquid pulp containing a large proportion of aqueousliquid and a small proportion of pulped fibrous material, such amount ofliquid pulp containing a predetermined weight of said fibrous material,draining and pulling out the major part of the aqueous liquid in suchpulp, by suction, encasing the residual semi-dried pulp material in apermeable envelope, supporting the package on a rigid perforated plate,applying a uniform mechanical pressure upon said package to squeeze outmore of the aqueous liquid, until a rigid damp pulp board is produced,placing such rigid damp board between nonflexible perforated members,capable of preventing warping of the board, and drying the board whileheld between said members to prevent substantial warping, whereby arigid board structure is produced.

In testimony whereof I afiix my signature.

ROBERT A. MARR.

